Electrowetting display devices are known. In an off state of a picture element of an example of such a device an oil layer covers a display area. In an on state the oil layer is retracted so as to cover less of the display area. To switch the picture element to the on state a voltage is applied via for example an electrically conductive fluid and an electrode, the conductive fluid being immiscible with the oil. To switch the picture element to the off state, the voltage is switched off.
Such a device may comprise multiple layers of different dielectric materials as a barrier layer between an electrode and the electrically conductive fluid.
It is desirable to improve the performance of such a barrier layer.